Force-Light-Heat Stimulation-Induced Multicolor Chromism and Multifunctional Applications of Europium Tungstate Phosphor

Stimulus-responsive chromogenic luminescent materials are promising for security and optical storage, yet force-induced color change in inorganic materials remains rarely reported. Here we report a europium tungstate that exhibits mechanochromism, driven by pressure-induced tungsten valence transformation and color center formation. The sample color shifts from orange to black with increasing pressure, accompanied by a linear variation in reflectance. A luminescence modulation rate of 100% for Eu3+ is achieved due to the strong reabsorption of the black state. Negative photochromism, switching from black/orange to white, occurs under laser irradiation or heating via the reversible phase transition between EuWO4 and Eu2W2O9. The luminescence modulation is attributed to the synergistic effects of body color reabsorption and nonradiative transitions. Our work demonstrates a robust inorganic material responsive to force, light, and heat, offering versatile functionality for pressure sensing, anti-counterfeiting, and optical storage, and provides a design strategy for multicolor chromogenic materials.

刺激响应型显色发光材料（Stimulus-responsive chromogenic luminescent materials）在防伪与光存储领域极具应用前景，但目前无机材料中力诱导变色现象的相关报道仍较为罕见。本文报道了一种具备力致变色（mechanochromism）特性的钨酸铕（europium tungstate），其变色行为由压力诱导的钨价态转变与色心（color center）形成共同驱动。随着压力升高，样品颜色由橙色逐渐转变为黑色，同时反射率（reflectance）呈线性变化。得益于黑色态的强重吸收效应，实现了Eu³+ 100%的发光调制速率（luminescence modulation rate）。在激光辐照或加热条件下，材料可通过EuWO₄与Eu₂W₂O₉之间的可逆相变（phase transition）发生负光致变色（negative photochromism）：由黑色/橙色转变为白色。该发光调制效应源于体色重吸收与非辐射跃迁（nonradiative transitions）的协同作用。本研究开发了一种可对力、光、热产生响应的稳定无机材料，可为压力传感、防伪及光存储提供多功能应用路径，同时为多色显色材料的设计提供了全新策略。